Electronics & Computers

This apparatus can measure high voltage safely and remotely.

An integrated optical voltage-measuring apparatus based on a Mach-Zehnder interferometer has been designed and constructed. The main feature of this apparatus is that optical fibers link part of it to an optical sensor head placed at the source of the voltage to be measured, whether the source be a space-based power distribution control system or a ground-based high-voltage system. The optical fibers and sensor of this apparatus are immune to electromagnetic interference. This apparatus could be highly suitable for use in automatic control of space-based or aeronautical power-management and power-distribution systems. Potential ground-based commercial applications include measuring voltages and electric fields in electrical power systems, physiological monitoring and recording, measurements of pulsed power, and testing for electromagnetic compatibility.

Optical measurement of voltage involves utilization of the linear electro-optic effect, also known as the Pockels effect. Previously developed electro-optical voltage sensors have incorporated bulk electro-optic crystals and such bulk optical components as lenses, beam splitters, and polarizers. Because of the deficiencies in the design and construction of these devices, they have proved to be difficult to implement in the field. The use of bulk optical components can lead to difficulties in miniaturization, inadequate stability in outer-space applications, and high manufacturing costs.

The present integrated optical voltage-measuring apparatus overcomes these deficiencies of electro-optical voltage sensors made from bulk optical components. This apparatus is capable of measuring quasi-dc and ac signals at frequencies up to 3 MHz. It displays the true root-mean-square values of signals up to 200 V full scale. Its error is less than 2 percent of the full-scale reading. The maximum safe peak potential that can be applied to the optical head of this apparatus is 1,000 V. This apparatus also provides an analog output that can be used to display the measured waveform on an oscilloscope. The optical voltage-sensing head and the rest of this apparatus can be separated by a fiber-optic cable for remote measurement of high voltage.

The outstanding features, benefits, and capabilities of this apparatus, in addition to those described above, are the following:

• Optical isolation,
• Measurement of continuous-wave and pulsed signals,
• Large dynamic range,
• No need for electrical power at the sensor head,
• Possibility of placing the sensor head in a hostile or harsh environment, and
• Safe measurement.

This work was done by Stuart A. Kingsley and Sriram S. Sriram of SRICO, Inc., for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4 – 8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-16731.